Hello Mikhail, you are the author of the patch eaf2aae18603965ff668384b391fcaa14de19823 in libraries/Cabal which you have merged into GHC HEAD on September 25 in the patch 4be50969491aa471d6c9ab3b9339036a355d45c6 The problem is that your patch breaks build on Solaris, here is the log from the Solaris/x86 builder: http://haskell.inf.elte.hu/builders/solaris-x86-head/178/10.html Could you be so kind and revert this patch or fix it to also work on Solaris? For Solaris the change should be easy, simply if you invoke Solaris' tar with --help, it'll fail with exit code 1 and help message printed into the stderr. If you are curious if it supports --format, then no. Please let me know if you are able to push fix or revert during next week or if I shall deal with it myself. I can't just fix that now myself since I'm overloaded with other tasks till Wednesday night... Thanks! Karel